{
"input": "225/60R16 98H",
"normalized": "225/60R16 98H",
"format": "metric",
"type": {
"code": null,
"name": "Passenger (Euro-metric / ISO)"
},
"construction": {
"code": "R",
"name": "Radial"
},
"aspectRatio": 60,
"width": {
"mm": 225,
"in": 8.86
},
"sidewall": {
"mm": 135,
"in": 5.31
},
"rim": {
"in": 16,
"mm": 406.4
},
"diameter": {
"mm": 676.4,
"in": 26.63
},
"circumference": {
"mm": 2125,
"in": 83.66
},
"revolutions": {
"perMile": 757,
"perKm": 471
},
"service": {
"loadIndex": {
"index": 98,
"kg": 750,
"lb": 1653
},
"speedRating": {
"symbol": "H",
"kmh": 210,
"mph": 130
},
"text": "98H"
},
"loadRange": null,
"approximate": false,
"notes": [],
"warnings": [],
"disclaimer": "Computed from the size code and public standards; nominal, unloaded dimensions. Not a safety recommendation: follow the vehicle placard (door jamb) and the tire maker's load and inflation tables."
}
curl --location --request GET 'https://zylalabs.com/api/14561/tire+size+decoder+api/37305/decode+a+tire+size?size=225/60R16 98H' --header 'Authorization: Bearer YOUR_API_KEY'
{
"from": "225/60R16 98H",
"to": "235/65R16 103H",
"diameter": {
"from": {
"mm": 676.4,
"in": 26.63
},
"to": {
"mm": 711.9,
"in": 28.03
},
"difference": {
"mm": 35.5,
"in": 1.4,
"percent": 5.25
}
},
"width": {
"from": {
"mm": 225,
"in": 8.86
},
"to": {
"mm": 235,
"in": 9.25
},
"difference": {
"mm": 10,
"in": 0.39,
"percent": 4.44
}
},
"sidewall": {
"from": {
"mm": 135,
"in": 5.31
},
"to": {
"mm": 152.8,
"in": 6.01
},
"difference": {
"mm": 17.8,
"in": 0.7,
"percent": 13.19
}
},
"circumference": {
"from": {
"mm": 2125,
"in": 83.66
},
"to": {
"mm": 2236.5,
"in": 88.05
},
"difference": {
"mm": 111.5,
"in": 4.39,
"percent": 5.25
}
},
"revolutions": {
"from": {
"perMile": 757,
"perKm": 471
},
"to": {
"perMile": 720,
"perKm": 447
},
"difference": {
"perMile": -37,
"perKm": -24
}
},
"speedometer": {
"unit": "mph",
"indicated": 60,
"actual": 63.1,
"errorPercent": 5.25,
"reads": "low (you are going faster than it shows)"
},
"odometer": {
"unit": "miles",
"shown": 100,
"actual": 105.25
},
"guideline": {
"maxDiameterDifferencePercent": 3,
"withinGuideline": false,
"note": "Within 3% of the original overall diameter is the common rule of thumb; the vehicle maker's approved sizes come first."
},
"warnings": [
"The overall diameter differs by 5.25% (more than the common 3% guideline): speedometer, ABS/stability control, gearing and clearance can be affected."
],
"notes": [],
"disclaimer": "Computed from the size code and public standards; nominal, unloaded dimensions. Not a safety recommendation: follow the vehicle placard (door jamb) and the tire maker's load and inflation tables."
}
curl --location --request GET 'https://zylalabs.com/api/14561/tire+size+decoder+api/37306/compare+two+sizes?from=225/60R16 98H&to=235/65R16 103H&speed=60&unit=mph' --header 'Authorization: Bearer YOUR_API_KEY'
{
"index": 98,
"kg": 750,
"lb": 1653,
"notes": [
"Maximum load per tire at the maker's reference inflation pressure. A P-metric tire on a light truck, SUV or trailer is derated by 1.10 in US practice."
],
"disclaimer": "Computed from the size code and public standards; nominal, unloaded dimensions. Not a safety recommendation: follow the vehicle placard (door jamb) and the tire maker's load and inflation tables."
}
curl --location --request GET 'https://zylalabs.com/api/14561/tire+size+decoder+api/37307/load+index+lookup?index=98' --header 'Authorization: Bearer YOUR_API_KEY'
{
"symbol": "H",
"kmh": 210,
"mph": 130,
"disclaimer": "Computed from the size code and public standards; nominal, unloaded dimensions. Not a safety recommendation: follow the vehicle placard (door jamb) and the tire maker's load and inflation tables."
}
curl --location --request GET 'https://zylalabs.com/api/14561/tire+size+decoder+api/37308/speed+rating+lookup?symbol=H&unit=mph' --header 'Authorization: Bearer YOUR_API_KEY'
{
"input": "DOT U2LL LMLR 2319",
"dateCode": "2319",
"format": "4 digits (2000 onward)",
"week": 23,
"year": 2019,
"manufactured": {
"weekStart": "2019-06-09",
"weekEnd": "2019-06-15",
"month": "2019-06"
},
"plantCode": "U2LL",
"asOf": "2026-10-16",
"age": {
"years": 7.4,
"months": 88
},
"warnings": [
"6 years or older: many vehicle makers advise replacing tires 6 years after manufacture, and annual inspection by a professional is commonly recommended from 5 years. Check the vehicle and tire maker's guidance."
],
"notes": [
"Week 01 is the first full Sunday-Saturday week of the year (49 CFR 574.5). The date code is on one sidewall only; look on both sides."
],
"disclaimer": "Computed from the size code and public standards; nominal, unloaded dimensions. Not a safety recommendation: follow the vehicle placard (door jamb) and the tire maker's load and inflation tables."
}
curl --location --request GET 'https://zylalabs.com/api/14561/tire+size+decoder+api/37309/decode+a+dot+date+code+tire+age?code=DOT U2LL LMLR 2319&asOf=2026-10-16' --header 'Authorization: Bearer YOUR_API_KEY'
After signing up, every developer is assigned a personal API access key, a unique combination of letters and digits provided to access to our API endpoint. To authenticate with the Tire Size Decoder API simply include your bearer token in the Authorization header.
| Header | Description |
|---|---|
Authorization
|
Required
Should be Bearer access_key. See "Your API Access Key" above when you are subscribed.
|
No long-term commitment. Upgrade, downgrade, or cancel anytime.
Decode tire sizes, compare sizes with speedometer error, load/speed ratings, DOT dates.
Each endpoint returns structured data related to tire sizes, including specifications like width, aspect ratio, load index, speed rating, and DOT date codes. For example, the "Decode a tire size" endpoint provides detailed tire dimensions and service descriptions, while the "Compare two sizes" endpoint highlights differences in size metrics.
Key fields include "input," "normalized," "width," "diameter," "service" (load index and speed rating), and "notes." For instance, the "Decode a tire size" response includes tire dimensions in both mm and inches, along with load and speed ratings.
Parameters vary by endpoint. For "Decode a tire size," you provide the tire size string. In "Compare two sizes," you specify two tire sizes to compare. The "Load index lookup" and "Speed rating lookup" endpoints accept specific index or symbol values, while "Decode a DOT date code" requires the DOT number.
Response data is organized in a JSON format with nested objects. For example, the "Compare two sizes" endpoint includes separate sections for diameter, width, and sidewall, each detailing "from" and "to" values, along with differences in mm, inches, and percentage.
The data is computed from tire size codes and public standards, ensuring it reflects nominal, unloaded dimensions. The API emphasizes that users should follow vehicle placards and tire maker's guidelines for safety and accuracy.
Typical use cases include determining compatibility of tire sizes for vehicles, assessing speedometer accuracy based on tire changes, and evaluating tire age for safety. Users can also check load capacities and speed ratings to ensure compliance with vehicle specifications.
Users can utilize the returned data to make informed decisions about tire purchases, replacements, and maintenance. For example, comparing tire sizes helps assess potential impacts on vehicle performance, while DOT date codes inform users about tire age and safety recommendations.
If a request returns partial or empty results, users should verify the input parameters for accuracy. For instance, an invalid tire size may yield a 400 error. Users can also refer to the API documentation for guidance on valid input formats and expected outputs.
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